CN101689350B - Method and system for driving a backlight in a display - Google Patents

Method and system for driving a backlight in a display Download PDF

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Publication number
CN101689350B
CN101689350B CN200880023378.6A CN200880023378A CN101689350B CN 101689350 B CN101689350 B CN 101689350B CN 200880023378 A CN200880023378 A CN 200880023378A CN 101689350 B CN101689350 B CN 101689350B
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Prior art keywords
backlight
display
light source
distribution
light
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CN101689350A (en
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F·P·M·布德泽拉尔
A·多米斯
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Koninklijke Philips NV
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Koninklijke Philips Electronics NV
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G09G3/342—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
    • G09G3/3426—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines the different display panel areas being distributed in two dimensions, e.g. matrix
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0613—The adjustment depending on the type of the information to be displayed
    • G09G2320/062—Adjustment of illumination source parameters
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • G09G2330/021—Power management, e.g. power saving
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2360/00—Aspects of the architecture of display systems
    • G09G2360/16—Calculation or use of calculated indices related to luminance levels in display data

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Liquid Crystal (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)

Abstract

A backlight control system for controlling a backlight of a display. The display (100) comprises a transmissive display panel (102) and a backlight (104) for providing an illumination to a backside (108) of the display panel. The backlight comprises light sources (110) positioned at light source positions for providing illumination to the backside of the display panel. The system comprises a drive value generator (106) for providing light source drive values (112) for causing the backlight profile to gradually descend around a high luminance portion of the display at a rate that is independent of a position of the high luminance portion with respect to the light source positions. The high luminance portion of the display has a higher luminance than an area around the high luminance portion of the display. The system allows to prevent a disturbing perception of backlight structure and halo.

Description

The method and system that is used for the backlight of driving display
Technical field
The present invention relates to the backlight of display.
Background technology
Conventional LCD TV and LCD computer monitor comprise transmission-type LCD panel and backlight, and said backlight is generated to the pattern of the more or less even and constant luminance on the LCD panel dorsal part.The LCD panel becomes desirable color and brightness to produce the reproduction of image this optical modulation.
In SID Symposium Digest of Technical Papers, Society for InformationDisplay, in June, 2006; The 37th volume, the I phase is in the 1520-1523 page or leaf; In " the 44.4:RGB-LED Backlights for LCD-TVs with OD; ID, and 2D AdaptiveDimming " of T.Shirai, the RGB-LED backlight of the LCD-TV that has 0D, 1D and the light modulation of 2D self-adaptation has been discussed.The output brightness of RGB-LED backlight that is used for LCD-TV with 0D (evenly light modulation), 1D (line light modulation) and 2D (local dimming) mode in company with incoming video signal light modulation adaptively.Select dim factor to make become identical with original image of the image of institute's perception after the self-adaptation light modulation; And equal to be used to drive this LC module to greatest extent back the becoming of light modulation operation, and also make the total power consumption of backlight unit become minimum corresponding to the maximum vision signal in all LCD pixels of this block.When calculating said maximum vision signal, also consider the gamma characteristic of LCD module and the light leak through the LCD module.
This self-adaptation light adjusting system allows to improve.
Summary of the invention
The improved procedure that advantageously has control display backlight source.In order to address this problem better, in first aspect of the present invention, a kind of system that controls the display backlight source is proposed, wherein this display comprises:
Transluscent display panel; And,
Be used for providing the backlight of illumination to the dorsal part of this display panel; This backlight comprises a plurality of respective sources that are positioned corresponding preset light sources position; Be used for to the corresponding lap of the dorsal part of this display panel illumination being provided according to corresponding preset light sources Luminance Distribution; Wherein can come the intensity that light-source brightness distributes is carried out convergent-divergent (scalable), and the stack of wherein (scaled) light-source brightness distribution of corresponding convergent-divergent have defined distribution backlight by means of the light source motivation value.
This system comprises:
The motivation value generator; It relies on corresponding to will the light source motivation value being provided by the brightness of image value of display images displayed; This motivation value generator is arranged to make distribution backlight to descend gradually around the hi-lite of display with given pace; This speed is independent of the position of this hi-lite with respect to light source position, and the hi-lite of this display has the brightness higher than the hi-lite peripheral region of display.
Through the dependency graph image brightness backlight intensity is set partly and controls backlight intensity.This allows to reduce the power attenuation of backlight, because no longer need always keep the full intensity that is in backlight.And, with display in comparison backlight, backlightly can further reduce power attenuation through reducing partly in the low position of brightness of image with possibility decay.And this embodiment allows enhancing contrast ratio, because provide low-light level backlight to dark image section.This is provided with low-intensity through the position that has low-light level at image and allows to form darker district and through the position that has high brightness at image high strength is set and allow to form brighter district.
Because because technical restriction transluscent display panel is not opaque fully in dark areas, some in the light that these dark areas provide still can be seen by the beholder.This effect is known as haloing.Descend gradually around hi-lite through making distribution backlight be independent of light source position, this haloing effect becomes and does not make the beholder vexed so.Resulting image more can attract the beholder.Improved the general image quality of watching.
In an embodiment, the motivation value generator comprises:
Be used for establishing the device of the corresponding candidate motivation value of respective sources based on the brightness of the predetermined portions of the image on the predetermined portions of display to be shown; Wherein candidate's motivation value is corresponding to the light source motivation value; Said light source motivation value will make backlight generate predetermined distribution backlight when being applied to backlight; This predetermined this predetermined portions that is distributed in display backlight has high-high brightness and descends gradually around this predetermined portions of display with set rate; Said set rate is independent of the position of this predetermined portions of display with respect to light source position, and the device that wherein is used to establish candidate's motivation value is arranged to establish candidate's motivation values to obtain to be used for a plurality of candidate's motivation values of one of them light source with respect to a plurality of predetermined portions of image; And,
Rely on said candidate's motivation value and establish the device of the light source motivation value of this one of them light source.
This is the efficient way of distribution backlight that realization is hoped.Predetermined portions through based on image is established candidate's motivation value, organizes calculating with efficient way.The motivation value generator can be arranged to use the maximal value in candidate's motivation value of establishing to light source.Similarly, also can use minimum value or mean value or average.And, can use any function of candidate's motivation value, such as statistical function.
In an embodiment, the device that is used for establishing the light source motivation value comprises and being used for to the device of this one of them light source in candidate's motivation value establishment maximum drive value.This has guaranteed that backlight illumination can be not low excessively.
In an embodiment, predetermined distribution backlight has the shape of the amplification shape of representing the light-source brightness distribution.
In an embodiment, predetermined distribution backlight has five times limited radius less than distance between two light sources.In this way, only the light source of limited quantity need contribute to predetermined distribution backlight.This has reduced the required amount of calculation of calculating motivation value.And, also strengthened contrast because to the position that needs light and only around it limited zone light is provided partly.Remaining display area keeps not being illuminated, and this causes the improved reproduction of dark object.Preferably, predetermined distribution backlight has 2 times the limited radius at the most of distance between two light sources.Preferably, predetermined distribution backlight has 1.5 times the limited radius at the most of distance between two light sources.
In an embodiment, the device that is used to establish candidate's motivation value comprises:
The predetermined portions that is used to rely on display is established the device of weights with respect to the position of one of them light source position; And,
Be used to calculate the device of product of value of the predetermined portions brightness of weights and representative image.
Weights are to calculate light source to form the practical of the required motivation value of virtual distribution and mode efficiently.They allow in look-up table, to calculate in advance weights.
In an embodiment, the device that is used for establishing the device of weights and is used to calculate product is arranged to be applied to the appropriate section of a plurality of predetermined portions of display, and the number of predetermined portions is greater than the number of light source.The number metaphor ground of predetermined portions is corresponding to the number of virtual light source, and each virtual light source produces virtual light source and distributes.Owing to a large amount of predetermined portions is arranged, so simulate a large amount of virtual light sources.Therefore, as if for the beholder, the number of light source is greater than the actual light source number.
In an embodiment, the motivation value generator comprises that the brightness of the predetermined portions that is used for the dependency graph picture in having difform a plurality of predetermined distribution backlight, selects the device of predetermined distribution backlight.This allows the more multiselect item of fine setting backlight control system.
In an embodiment, if at least one in the brightness of image value surpasses predetermined threshold, then select distribution predetermined backlight, to increase the maximal value of being scheduled to distribution backlight with flat top.Distribution with flat top allows more light sources to use with its maximum intensity.In this way, can increase the total brightness at the given spot place of display.This is particularly suitable for little high brightness spot.
Embodiment comprises a kind of display, and this display comprises:
Transluscent display panel;
Described backlight; And,
Comprise backlight control system like described motivation value generator.
Display panel can comprise the LCD panel.Light source can comprise LED.
Display can be the part of TV or computer monitor.
Embodiment comprises the method in control display backlight source, and this method comprises:
Dependence is corresponding to will the light source motivation value being provided by the brightness of image value of display images displayed; This motivation value generator is arranged to make distribution backlight to weaken gradually around the part of display with the speed that is independent of light source position, and this part that accordings to this display of brightness of image value comprises the brightness higher than this part peripheral region of display.
Embodiment comprises the computer program that is used to control the display backlight source, and this computer program comprises the instruction that is used for following operation:
Dependence is corresponding to will the light source motivation value being provided by the brightness of image value of display images displayed; This motivation value generator is arranged to make distribution backlight to weaken gradually around the part of display with the speed that is independent of light source position, and this part that accordings to brightness of image value display comprises the brightness higher than this part peripheral region of display.
Description of drawings
Referring to accompanying drawing, further set forth and described these and others of the present invention, in the accompanying drawings:
Fig. 1 provides the impression of the instance of the light that is generated by the tunable optical backlight;
Fig. 2 is the diagram of embodiment;
Fig. 3 illustrates the reproduction of speck point;
Fig. 4 illustrates the reproduction of speck point;
Fig. 5 illustrates the Luminance Distribution of light source;
Fig. 6 illustrates two kinds of layouts of light source;
Fig. 7 illustrates distribution overview backlight;
Fig. 8 illustrates some distributions backlight;
Fig. 9 illustrates some distributions backlight; And
Figure 10 is the diagram of embodiment.
Embodiment
Conventional LCD display system comprises backlight, and backlight generates the uniform luminance pattern on the dorsal part of LCD, and afterwards, the LCD panel becomes desirable image with this optical modulation.Backlight light-adjusting is based on following design: backlight itself also can be modulated, thereby only generate light in position that needs light and time.
The optimal design of 2D light modulation back light system relates to a large amount of compromise, and depends on wide in range design object set.Four major reasons using the 2D light modulation are to save power, local peaking, contrast and visual angle to improve.
But the 2D light modulation may be introduced pseudomorphism, for example: the haloing around bright object, visible backing structure and color and/or luminance non.
When being designed for the system of control 2D dimming characteristic, existing and save power and alleviate trading off between the pseudomorphism.For example, the type of used LCD panel is depended in this selection: if use can with the backlight intensity panel of well reproduced dark areas irrespectively, to reduce will be important relatively to power so.Otherwise alleviating usually of backing structure pseudomorphism is more important.
Preferably, in backlight, use a large amount of relatively LED.When in backlight, using a large amount of LED, can improve contrast; So, narrow so that owing to human visual system's restriction is hidden to the haloing that light caused of dark areas with regard to enough by " leakage ".
When only using a small amount of LED, still can realize saving the target of power and/or local peaking.
Can realize some modification of backlight light-adjusting system.In being known as first modification of 0D light modulation, this backlight still generates the uniform luminance pattern, but modulates its intensity based on the requirement of deriving from video content.Signal to the LCD panel must also be modified the output backlight with the compensation modulation.Some advantage of 0D light modulation is:
The power consumption of-reduction: backlight needs less power to reproduce than dark scene.
-improved contrast, particularly for dark scene: if backlight level is lower, LCD light is revealed less.
Improve at-visual angle, particularly for dark scene.For low transmission value, the LCD performance is not good enough.Through light modulation, the LCD transmission value will be higher with compensation weaken backlight.In this way, the character of high transmission LCD also will be applicable to than dark scene at present.
Above-mentioned advantage also is applicable to 1D light modulation and 2D light modulation, and 1D light modulation and 2D light modulation will define hereinafter.
Horizontal bar or the vertical bar that can modulate separately that be divided into backlight represented in the 1D light modulation.The 1D light modulation all is improved aspect all three with respect to the 0D light modulation.And when panel had the total power consumption limit, if total lightness (brightness) is enough low, then it became and can reproduce higher peak value lightness.
Although can use vertical bar, usage level bar preferably.Fluorescent light is when when horizontal level is operated, tending to work best.And most of natural scene tends to have cut apart (for example just as in the having the landscape scene of sky) of suitable horizontal alignment, and for this situation, the vertical fragmentation performance is better.
Utilize the 2D light modulation, the segment that to control separately that is divided into backlight.Fig. 1 illustrates the impression of the light that is generated by this 2D tunable optical backlight.Equally, this all is improved aspect all four with respect to the 1D light modulation.
For (for example) conventional cold-cathode fluorescence lamp (CCFL), can carry out 0D and 1D light modulation, but this lamp only has limited depth of modulation.The 2D light modulation needs small light source, for example light emitting diode (LED).
Fig. 2 illustrates the example architecture of light modulation LCD system.This generic structure is effective for 0D, 1D and 2D system.Input signal 1 has been described image to be reproduced.For example, it has used data format descriptor known in the art for the target strength of red, the green and blue channel of each pixel in this image.LED motivation value generator 2 relies on input signal 1 and derives series of LED motivation value 3, and this series of LED motivation value 3 is used for driving LED backlight 4.This will generate light pattern 5 on LCD panel 10, and the brightness space that has according to the LED motivation value distributes.This light is modulated to realize the target image 11 corresponding to input signal 1 by LCD.In order to derive suitable LCD motivation value 9, the second processing path is provided.Analogy unit 6 provides the light intensity of simulation to obtain to provide to the LCD panel in physics LED-backlit source 4.Therefore, the light that in analogy unit 6, calculates actual generation according to LED motivation value 3 distributes 7.The light distribution of this actual generation is provided to LCD motivation value generator 8.This LCD motivation value generator 8 makes the input signal of using up distribution 7 and description image to be generated come to the LCD panel motivation value to be provided.For example, LCD motivation value generator 8 with pixel and at this pixel place with the color intensity of the image that generates to reality execution backlight cut apart.
In order to allow suitably to form desirable image, optimal algorithm selection ground used in LED motivation value generator 2 is arranged to generate motivation value 3, and the light 5 that motivation value 3 generates backlight 4 is enough to allow LCD panel 10 that light 5 is decayed to appropriate value 11.
In order to realize that maximum power reduces, LED motivation value generator 2 can select motivation value make its minimize motivation value 3 with, still satisfying the light 5 that is generated by backlight 4 simultaneously is enough to allow LCD panel 10 light 5 to be decayed to the requirement of appropriate value 11.
LED motivation value generator 2 need not to perfect, as long as the backlight intensity that provides minimum to need.Not good enough slightly but algorithm that be easier to implement also can obtain preferable image.But preferably, analogue unit 6 is very accurately.Any difference between the luminance distribution that analoging brightness distributes and reality generates can be used as the luminance errors in the final picture and becomes visible.
In image, exist the efficient of light modulation (particularly 0D light modulation) under the situation of less speck point maybe be limited.Under these circumstances, a kind of compromise soft limiting (soft-clipping) that can be to use reduces these regional lightnesses with the raising power efficiency, and improves the performance in the dark areas.
To one of reason of carrying out light modulation backlight is to increase contrast: even when use has the panel of poor contrast, do not generate the light time when originally, and light can not see through its and reveal, and obtain extremely high system contrast.But the LED-backlit source can not generate light distribution arbitrarily on the LCD panel.It receives the restriction of the expansion of light to the LCD panel of tissue and the LED of the LED that is generally matrix.
When generating the required light time of bright area, some that is generated in the light possibly be provided to adjacent dark areas.This light will partly see through LCD and reveal, and therefore, around bright object, may generate " haloing " of faint light.Fig. 3 illustrates this situation (exaggerating) instance.Fig. 3 illustrates the reproduction 302 of using the low contrast panel to utilize non-light modulation backlight, and it reproduces white point on black background.Reproducing 304, using identical panel but utilize 2D light modulation backlight that the identical white point on the black background is shown.Can recognize and when using the light modulation backlight, around white dirt, have haloing.Can recognize that also contrast is better when using the light modulation backlight: compare with the reproduction 302 that utilizes non-light modulation backlight to produce, produce darker district.
The existence of haloing need not to become problem.Human eye has limited local contrast scope, and the details in therefore adjacent with the clear zone dark space is sightless.Therefore, as long as this haloing has finite width, it is sightless that it is still (almost), perhaps is that human viewer is acceptable at least.
But this haloing may faintly illustrate backing structure, for example, and the light source arrangement of backlight.Fig. 4 illustrates the instance of this situation.Can find out that in Fig. 4 the right-hand somewhere of backlight intensity on speck point is maximum.For still image, this possibly be difficult to see, but when illustrating when moving scene, the haloing shape around bright area will be along with position change.This perception is tedious.
The two is relevant for the visuality that perception test demonstrates haloing and (relatively) width of haloing and contrast difference.Narrow haloing is difficult to see, even also be like this under the very poor situation of local black level therein (black level).This is because human visual system's restriction causes.Near bright area is covered dark areas.When the observer watched point source (for example, bright LED), vision system was introduced (non-existent) haloing around it.But brain is trained to ignores this haloing.The observer will only can see haloing when he makes great efforts to do so consciously.
This obtains to draw a conclusion.If the haloing width of being introduced is retained in the shaded areas, then the shape of haloing is very not relevant with lightness, because the observer will note shape and lightness less than haloing.If but wider width is preferably limited by the contrast reduction that haloing causes; Otherwise it will be visible.And the shape of haloing should not depend on the position on panel.Should be noted that pseudomorphism that normal television-viewing distance can't see near may become visible when watching display.
In haloing width and backlight, there is direct relation between the LED number.To such an extent as to if the contrast of panel so poor haloing will be visible, so preferably use the LED of sufficient amount to make that the haloing of being introduced is enough narrow and be not noted with maintenance with correct distribution.
Under the situation of introducing LED, can drive three (or more) primary colours that generate by backlight individually.This can be used for these colors are carried out independent light modulation, with further reduction power consumption and enhancing contrast ratio.
One of factor that influences 2D light adjusting system result is the shape that LED projects the Luminance Distribution on the LCD panel.Although have the concrete angle component of the position of depending on lcd screen by the light that LED generated, can use diffusing globe (diffuser) to remove this component.And, preferably, optics is provided so that arrive LCD panel polarization before at it by the light that LED produced.
Term LED distributes and is used to represent to project the intensity distributions of the polarized light on the LCD panel.In this document, only described circular distribution in detail.But it will be understood by a person skilled in the art that and can method and system as herein described be expanded to non-circular distribution.
Suppose that the position on the LCD in LED dead ahead panel is this center of distribution.Apart from r is position and the distance between this center on the LCD.Brightness L can be described as L (r) at present.
Can distinguish two types of distributions.The unlimited distribution illustrates the higher value for r, and L (r) diminishes, but never is 0.The gaussian sum Lorentz is distributed as infinitely distributive instance.But limited distribution has parameters R, i.e. distribution radius.For r＞R, brightness is 0 (or at least very little).Fig. 5 illustrates the instance of the limited distribution of R=1.5.Its between the position and the distribution center that illustrate on the transverse axis on the LCD panel apart from r.It illustrates the lightness that is provided by LED with arbitrary unit on Z-axis.Limited distribution has interesting character.Because limited scope,, only must consider than R to make algorithm simpler more near the LED of specified point on the LCD panel when calculating the light time that amounts to.And when the black region distance is enough far away than bright area, black region will be very dark.If light scatters on big zone (big R), the shape of haloing will be very soft, just look at less than backing structure.
If distribution shape is limited (little R), only a few LED will contribute to particular location, and the haloing width will be narrow.Can realize the peak value lightness through only connecting a few LED.But it can illustrate backing structure.Narrow distribution can cause higher power to reduce.And because less LED contributes to ad-hoc location, calculate in the light quantity of this position and only need consider less LED set, make that calculating is easier.
In principle, LED can any mode easily arrange.For 1D and 2D tunable optical system, the flatness of distribution and LED arrange closely related, particularly for narrow distribution.In this field (area), symmetric arrangement has advantage.And symmetric arrangement has reduced the computational complexity of algorithm.Therefore, preferably, being symmetrical set of LED is used for 1D and 2D light adjusting system, for example, square 602 with equilateral triangle 604.It is all shown in Fig. 6.The advantage of square 602 layouts is, because its symmetric property, it allows relatively easily to place the direct reflection border.
Can be described below and realize that backlight projects the simulation of the light on the LCD (frame 6 of Fig. 2) with it.Suppose that N is the number of pixels of LCD, and M is the number of LED in the backlight.There is attenuation coefficient A in each path for from LED to pixel Ij, it depends on that LED distributes and the distance from this LED to pixel.Light L by pixel j reception jThe summation that multiply by attenuation coefficient through the light that is sent by LEDi obtains:
L j = Σ i = 1 M A ij L i .
But this formula needs relative great amount of calculation.Can be through for example using symmetry, limited LED distribution radius to simplify and needing to allow less error so that calculated amount and required storage are reduced to manageable amount.
In implementing LED motivation value generator (frame 2 among Fig. 2), there is the LED motivation value of freedom optimize to(for) objectives.Preferably, LED motivation value generator 2 guarantee that each pixel receives it at least should be according to the light quantity of input signal 1 transmission.This can carry out through separating one group of inequality.If V jThe light quantity of the minimum needs of pixel j has been described, so:
V j ≤ Σ i = 1 M A ij L i .
Preferably, select A IjMake always to exist at least one to separate for this group inequality, that is, wherein all LED are with the situation of its maximal value (that is, not using light modulation) driving.But, have unlimited a plurality of separating usually.Find and/or select optimum solution to depend on embodiment.
When the intrinsic contrast of LCD panel and when not really high, will see through also the panel in dark areas and reveal (as illustrating) in digital 302 places from the light of backlight.This itself possibly be tedious.But visible static backlight structure (as shown in fig. 4) is troublesome more.In pan (panning scene), this static structure will cause " dirty window (dirtywindow) " effect, and this can make the image quality degradation.Therefore, a target can be and minimizes the visuality that backlight LED is arranged.There are at least two kinds of key elements that this visuality is contributed.The physical Design of backlight is one, comprises like character such as LED spacing, light mixing, the dispersions of distribution.If but drive inadequately, also possibly show relatively poor even design good backlight.Therefore, be used for also contributing to making system show optimum level from the algorithm of video information derivation motivation value.
In principle, exist one of LED motivation value that minimal power consumption is provided to separate the perhaps set of separating of same performance.In order to reduce computational complexity, can use approximate that minimal power consumption separates.Should be noted that minimum pseudomorphism and minimum power method can obtain significantly different result.
Ideally, LED motivation value generator is considered the motivation value of each pixel on the lcd screen individually.Current HDTV screen (1920 multiply by 1080 pixels) is a characteristic with about 2,000,000 pixels, this means to handle mass data to achieve this end with very high speed.In order to reduce computational complexity, for the purpose that the LED motivation value generates, image can be down sampled to more manageable size, and for example, the area to 192 * 108 has reduced 100 times with calculated amount, and only introduces marginal error.Preferably, the high-high brightness level in the use pixel region in downsampled version.This General Principle can be applicable to the embodiment of all descriptions of LED motivation value generator.
LED motivation value generator also can distribute and simplifies than the actual physics simple LED that distributes more through hypothesis.When using for any position prediction, will satisfy following requirement based on the result of this algorithm: should always have enough at least light at any location of pixels than the distribution of actual distribution light still less.Preferably, analogue unit 6 uses actual physics to distribute the actual strength backlight of calculating pixel position.This permission generates LCD motivation value more accurately by LCD motivation value generator 8, and this can cause better reproducing 11.This simplification can make that the power efficiency of system is slightly poor.But this algorithm can become and be easier to implement and more cheap aspect calculating.
In the embodiment of LED motivation value generator 2, adopt quite efficiently and simple algorithm extremely.In order to obtain concrete lightness, (all LED in the r＜R) are enough to connect the scope that identical motivation value for use drives.If other zone needs another lightness of LED, then take the maximal value of motivation value.But when bright object moved (so shift-in shifts out the zone that is limited radius R) everywhere on screen, this driven algorithm can illustrate violent " beating " of motivation value.And haloing is relatively large and the LED dot structure can be shown.
In another embodiment of LED motivation value generator 2, slightly more complicated but algorithm that have more power efficiency is true below utilizing: the LED near the position that needs light is the most employed LED.Each position is handled in regular turn.Calculate motivation value according to institute's light requirement near the LED of this position.If required motivation value less than 100%, can generate enough light by this LED, and can continue this algorithm for the next position.If it is higher than 100%, this value is limited to 100%, and uses next hithermost LED to generate the light of disappearance.Continue like this up to generating enough light.But when bright object moved on screen everywhere, this driven algorithm also can illustrate violent " beating " of motivation value.
In another embodiment of LED motivation value generator 2, use the expansion of the previous algorithm of describing.It is worked with a plurality of operations (pass).At first procedure, calculate the motivation value of hithermost LED.This value is clipped to 100%.In all motivation values for specific LED calculating, the storage mxm..In second operation work, calculate the intrinsic brilliance level of each pixel based on the LED motivation value of being stored.For most of LED, luminance level will be equal to or higher than needed level at present.But some pixel possibly still can not receive enough light.In order to overcome this point, calculate new (higher) motivation value for second hithermost LED (hithermost LED has been 100% unlatching).Repeat this process and receive enough light up to all pixel-by-pixel basis.
In another preferred embodiment of LED motivation value generator 2, use the algorithm of the low visuality that backing structure is provided.This algorithm is based on following design: can distribute with the virtual LED that is associated by any any position simulation virtual LED on screen through driving physics LED with suitable motivation value.For example, each pixel can have its oneself virtual LED.One group of coefficient is associated with each virtual LED of the ratio of describing physics LED contribution on every side.Fig. 7 illustrates the one-dimensional representation of the distribution of five LED that utilize the diverse location place that the different driving value drives with curve map 704.In curve map 702, the virtual distribution of gained is shown.Curve map 702 and 704 is illustrating the position and brightness is being shown on Z-axis on the transverse axis.Can find out that virtual distribution 702 reaches maximal value between the maximal value of two adjacent independent physical distribution.Through driving LED suitably, the maximal value of virtual distribution can optionally be positioned any position.
Fig. 8 illustrates three width of cloth curve maps that have in position on the transverse axis and the brightness on Z-axis.It illustrates three different distributions backlight (perhaps ' virtual LED ') 802,804 and 806 with curve map A, curve map B and curve map C, and they have their maximal value at the diverse location place with respect to the fixed position of four LED (Led1, Led2, Led3 and Led4).Distribution 802,804,806 backlight is of similar shape, but is in the position of displacement.The shape of distribution backlight and fall off rate and distribution backlight are with respect to the location independent of light source position led1, Led2, Led3, Led4.The light of in curve map A, B and C, also having drawn each LED distributes 808.For the maximal value 810,812,814 that the difference of distribution 802,804,806 backlight is located, the photodistributed amplitude of each LED is different.Consider the instance of the Led2 in the distribution backlight of curve map A, can be for example calculate the weights or the coefficient of the candidate's motivation value that is used to calculate Led2 through the peaked height that removes light distribution 808 with the maximal value 810 of distribution 802 backlight.
In order to produce the concrete brightness of virtual LED, preferably utilize the required motivation value of virtual LED to multiply by the predetermined coefficient value that is associated and drive physics LED.But the said coefficient of calculated off-line is because they are from deriving such as physical parameters such as distribution, intervals.
Algorithm according to embodiment is worked as follows:
For each virtual LED, confirm required brightness.This required brightness is preferably according to the object brightness of input signal 1 based on the center of virtual LED.The motivation value of the physics LED of calculations thus.Because a physics LED contributes to many virtual LEDs, also there are many motivation values of calculating to this physics LED.Use maximal value in these values as the actual drive level of LED.
In order to reduce computing cost, can limit the number of virtual LED.Substitute virtual LED of each pixel, can use each virtual LED in zone.In the case, calculate the intensity of virtual LED through the high-high brightness that obtains the pixel in the zone.Use the zone also to reduce the required memory space of coefficient table.
Preferably, little peak handling (headroom) value is added to (physics or virtual) LED intensity, therefore can temporarily surpass the maximum drive value driving LED.This helps to consider any unevenness that LED distributes in this zone.
Produce these zones through meticulousr grid being divided into by the grid that physics LED forms.Then, each zone is related with vertical phase place (phase) with the level with respect to physics LED grid.For example, if the horizontal line between two physics LED is divided into four step levels (step), will have four phase places so.If in vertical direction, accomplish same operation, then define 16 zones, each zone has specific x and y phase place and the pre-determined factor table that is associated.
Use these zones, virtual LED still illustrates (meticulous) geometry, although less than original physics LED spacing.Therefore do not generate light at location of pixels definitely yet.Under the situation of bright object of which movement, the virtual LED motivation value can be beated when object is crossed over the border between the zone slightly.Preferably, between the visuality of grid and number of phases to be performed, make compromise.
, realize all LED that contribute maximum optical output when driving horizontally openable with 100%.When only having the zonule of a maximum lightness, it will be in the peak value of virtual distribution, and the physics LED that contributes all opens with 100%, and therefore light output will be lower than maximum attainable value.Therefore, the zonule of maximum lightness possibly not be able to optimally reproduce.There is some mode of offsetting this effect.At first, the maximum lightness of LED can increase (using built-in peak handling).Secondly, can prevent use whole 100% obtainable lightness.The 3rd, can reduce the lightness of little bright area.The 4th, can change the driven algorithm of little bright area, thereby introduce bigger haloing for those little bright area.The 5th, can increase the width that virtual LED distributes.
Although physical distribution is preferably level and smooth, can more freely select the shape of virtual distribution.Widen virtual distribution and reduce the power reduction, but reduce required peak handling.Therefore introduce flat top for virtual distribution:, guarantee that hithermost LED is all used almost equally in order to produce this distribution through physical distribution is added up to.
Fig. 9 illustrates through the lightness level that reaches as required and comes the shape of adaptive virtual distribution to reproduce the mode of speck point with permission.On transverse axis, this curve map has the distance apart from virtual distribution center, and on Z-axis, this curve map has lightness.Two axles are arbitrary unit.This illustrates with the virtual distribution with low lightness top and compares, and the virtual distribution with high lightness top has the flat top of relative broad.Preferably, allow that in the maximum lightness of little bright object and the maximum of haloing selection is compromise between the visuality.
Should be pointed out that between physical distribution and virtual distribution not have man-to-man relation, because virtual distribution is by physical distribution and coefficient A IjConfirm.But be not all physics and virtual LED distributed combination be same suitable.By physical distribution be similar to the virtual distribution of target.Peak value and mean square of error root be any given approximate show what kind of indication.
Figure 10 illustrates the rough schematic view of embodiments of the invention.This illustrates display 100, and it comprises transluscent display panel 102, but LCD display panel and have the self-adaptation light modulation backlight 104 of the light source 110 of a plurality of tunable optical for example.In context, light source is meant of the backlight that can independently control its brightness.The light source 110 of backlight 104 provides light 808 to the dorsal part 108 of transluscent display panel 102.Display panel 102 will be become desirable color, the image that its qualification will be reproduced by the optical modulation that backlight 104 provides under the control of display panel controller 124.Display 100 comprises that input can temporarily be stored in the image 114 in the storer in the display to receive.
Light source 110 is positioned corresponding preset light sources position; Be used for to the corresponding lap of the dorsal part 108 of display panel illumination being provided, wherein can come the intensity that light-source brightness distributes is carried out convergent-divergent by means of the light source motivation value 112 that provides by motivation value generator 106 according to corresponding preset light sources Luminance Distribution 808.Light on the dorsal part 108 of the display panel that is produced by light source 110 forms distribution backlight.
Motivation value generator 106 provides light source motivation value 112.It is based on corresponding to confirming the light source motivation value by the brightness of image value of display institute images displayed 114.Image 114 can comprise the high-brghtness picture images part, and the zone around this high-brghtness picture images part of its brightness ratio is high.In the case, motivation value generator 106 makes distribution backlight descend gradually around the hi-lite of the display of exhibit high brilliance image section above that.Fall off rate is independent of the position of hi-lite with respect to light source position.
Motivation value generator 106 can comprise that the brightness that is used for based on the predetermined portions of the image on the predetermined portions of display to be shown establishes the device 116 of the corresponding candidate motivation value of respective sources.These candidate's motivation values are corresponding to the light source motivation value; Said light source motivation value makes backlight generate predetermined distribution backlight when being applied to backlight; This predetermined predetermined portions that is distributed in display backlight has high-high brightness and descends gradually around the predetermined portions of display with set rate, and this set rate is independent of the position of the predetermined portions of display with respect to light source position.
The device that is used for establishing candidate's motivation value is arranged to establish different candidate's motivation values to obtain a plurality of candidate's motivation values of one of them light source based on the brightness of the different predetermined portions of image.Device 118 is arranged to rely on the light source motivation value that candidate's motivation value is established this one of them light source.For example, in those candidate motivation values relevant, establish maximum drive value or minimum drive value with one of light source.
For example, predetermined distribution backlight has the shape of the amplification shape of representing the light-source brightness distribution.Preferably, predetermined distribution backlight has the limited radius of the limited multiple that is two distances between the light source.For example, this limited multiple is 5.For example, this limited multiple is 2.
In an embodiment, the device 116 that is used to establish candidate's motivation value comprises that the predetermined portions that relies on display establishes the device 120 of weights with respect to the position of the position of one of them light source.
Generator 122 is with the product of the value of the brightness of the predetermined portions of calculating weights and representative image.The output of this device 122 is candidate's motivation values.Perhaps, candidate's motivation value depends on the output of device 122.Preferably, this device 122 comprises a plurality of precalculated values.At least one the precalculated value in these a plurality of precalculated values is searched in the position of the position of predetermined portions one of them light source with respect to this of device 122 dependence displays.
Can provide control module the device that is used for establishing the device of weights and is used to calculate product to be applied to the appropriate section of a plurality of predetermined portions of display.For example, look-up table is provided, wherein stores precalculated value with respect to each position of each light source position for the predetermined portions of display.The entry number of look-up table can be removed equal value through the systematicness of using photodistributed symmetric property and light source position and reduced.
The number of predetermined portions is greater than the number of light source, because predetermined portions limits the center of ' virtual ' light source, and more substantial predetermined portions causes final distribution backlight is controlled in more detail.
Predetermined distribution can be not only by convergent-divergent.Can exist and have predetermined difform a plurality of predetermined distributions backlight.In an embodiment, the motivation value generator comprises that the brightness of the predetermined portions that is used for the dependency graph picture selects the device of one of these predetermined distributions backlight.
For example, if at least one in the brightness of image value surpasses predetermined threshold, then select distribution predetermined backlight with flat top.Compare with the distribution predetermined backlight of non-flat forms, this allows to increase the maximal value of virtual distribution backlight.
Randomly, analogue unit 126 is provided, it calculates the distribution backlight that is generated by backlight 104 according to the motivation value that is provided by motivation value generator 106.This distributed intelligence backlight is forwarded to display panel controller 124, and display panel controller 124 makes the motivation value of display panel adapt to the brightness that backlight 104 provides.
Display panel 102 can comprise the LCD panel, but it also can comprise any other transmissive display, for example based on the transmissive display of polymkeric substance.Light source 110 can comprise LED, but they also can comprise the light source of any other kind, such as fluorescent tube or conventional light bulb.
Display 100 can be the part of the display apparatus of TV, home entertainment system, portable television, computer monitor or any kind of.
In the method for the backlight 104 of controlling display 100; Dependence is corresponding to will the light source motivation value being provided by the brightness of image value of display images displayed; Thereby distribution backlight is weakened around the part of display with the speed that is independent of light source position gradually, and this part that accordings to brightness of image value display comprises the high brightness in peripheral region than this part of display.
Should be appreciated that the present invention also expands to computer program, the computer program on carrier or in the carrier particularly, it is suitable for realizing the present invention.The form of this program can be source code, object code, code intermediate source and object code, such as part compiling form, perhaps is applicable to enforcement any other form according to the method for the invention.Should also be clear that such program can have many different architecture designs.For example, implement according to the method for the invention or the degree code of the function of system can be subdivided into one or more subroutines.Many different modes of distribution function to those skilled in the art will be obvious in these subroutines.Subroutine can be stored in the executable file to form stand-alone program together.Such executable file can comprise computer executable instructions, for example processor instruction and/or interpreter instruction (for example, Java interpreter instruction).Perhaps, subroutine one or more or all can be stored at least one external libraries file and with master routine statically or dynamically (for example, in working time) link.Master routine comprises at least one at least once call in the subroutine.And subroutine can comprise the function call to each other.The embodiment relevant with computer program comprises the computer executable instructions corresponding to each treatment step at least one said method.These instructions can be subdivided into subroutine and/or be stored in can one or more files static or dynamically link in.Another embodiment relevant with computer program comprises the computer executable instructions corresponding to each device of at least one in said system and/or the product.But these instructions can be subdivided into subroutine and/or be stored in static linkage or one or more files of dynamic link in.
The carrier of computer program can be ability program-carried any entity or equipment.For example, carrier can comprise storage medium, such as ROM, and for example CD ROM or semiconductor ROM, perhaps magnetic recording media, for example floppy disk or hard disk.In addition, carrier can be the carrier that can transmit, and such as electric signal or light signal, it can or be carried through radio or alternate manner via cable or optical cable.When program was implemented in the sort signal, carrier can be made up of this cable or miscellaneous equipment or device.Perhaps, carrier can be the integrated circuit of the program that wherein embeds, and this integrated circuit is suitable for carrying out and perhaps is used to carry out correlation technique.
Should be noted that the foregoing description explanation the present invention and unrestricted the present invention, and under the situation of the category that does not depart from appended claims, those skilled in the art can design many alternate embodiments.In claims, place any Reference numeral between the bracket should not be considered to limit claim.Verb " comprises " and those listed in claims elements or the element outside the step or the existence of step are not got rid of in the use of version.The existence of a plurality of such elements do not got rid of in article " " before the element.The present invention can implement by means of the hardware that comprises some different elements and by means of the computing machine of suitable programmed.In enumerating the equipment claim of some devices, the some devices in these devices can be implemented by same hardware branch.This minimum true combination of not representing advantageously to use these measures of statement certain measures in different each other dependent claims.

Claims (16)

1. backlight control system that is used to control the backlight of display, said display (100) comprising:
Transluscent display panel (102); And
Being used for dorsal part (108) to said display panel provides the backlight (104) of illumination; Said backlight comprises a plurality of respective sources (110) that are positioned corresponding preset light sources position; Be used for to the corresponding lap of the dorsal part of said display panel illumination being provided according to corresponding preset light sources Luminance Distribution (808); Wherein can come the intensity that light-source brightness distributes is carried out convergent-divergent, and the stack of the wherein light-source brightness distribution of corresponding convergent-divergent have defined distribution backlight (802) by means of light source motivation value (112);
Said system comprises:
Motivation value generator (106); It relies on corresponding to light source motivation value (112) will be provided by the brightness of image value of said display images displayed (114); Said image comprises the high-brghtness picture images part; This high-brghtness picture images partly has than the regional high brightness around the said high-brghtness picture images part; Said motivation value generator is arranged to make said distribution backlight with the given pace hi-lite decline gradually on every side of the display of exhibit high brilliance image section above that; Said speed is independent of the position of said hi-lite with respect to said light source position, and the hi-lite of said display has than the regional high brightness around the hi-lite of said display.
2. system according to claim 1, wherein said motivation value generator comprises:
Be used for establishing the device (116) of the corresponding candidate motivation value of respective sources based on the brightness of the predetermined portions of the said image on the predetermined portions of said display to be shown; Wherein said candidate's motivation value is corresponding to the light source motivation value; Said light source motivation value will make said backlight generate predetermined distribution backlight when being applied to said backlight; The said predetermined predetermined portions that is distributed in said display backlight has high-high brightness and descends gradually around the predetermined portions of said display with set rate; Said set rate is independent of the position of the predetermined portions of said display with respect to said light source position, and the device that wherein is used to establish said candidate's motivation value is arranged to assign to establish candidate's motivation value to obtain a plurality of candidate's motivation values of one of them light source with respect to a plurality of reservations of said image; And
Be used to rely on the device (118) that said candidate's motivation value is established the light source motivation value of said one of them light source.
3. system according to claim 2, the device (118) that wherein is used for establishing said light source motivation value comprises the device that is used for establishing in candidate's motivation value to said one of them light source maximum drive value.
4. system according to claim 2, wherein said predetermined distribution backlight has the shape of the amplification shape of the said light-source brightness distribution of representative.
5. system according to claim 2, wherein said predetermined distribution backlight has five times limited radius less than distance between two light sources.
6. system according to claim 2, the device that wherein is used to establish said candidate's motivation value comprises:
The said predetermined portions that is used to rely on said display is established the device (120) of weights with respect to the position of the position of one of them light source; And
Be used to calculate the device (122) of weights and the product of the value of the brightness of the predetermined portions of the said image of representative.
7. system according to claim 6, the device that wherein is used to establish said weights comprises:
A plurality of calculated values in advance, and
At least one device of calculated value in advance that the predetermined portions that is used for relying on said display is searched said a plurality of calculated values in advance with respect to the position of the position of said one of them light source.
8. system according to claim 6, the device that the wherein said device that is used for establishing weights and said is used to calculate product is arranged to be applied to the appropriate section of a plurality of predetermined portions of said display, and the number of predetermined portions is greater than the number of light source.
9. system according to claim 2, wherein said motivation value generator comprises that the brightness of the said predetermined portions that is used for relying on said image selects the device of predetermined distribution backlight in having difform a plurality of predetermined distribution backlight.
10. system according to claim 9, if at least one in the wherein said brightness of image value surpasses predetermined threshold, the distribution of selecting so to have flat top predetermined backlight is to increase the maximal value of said predetermined distribution backlight.
11. a display, it comprises:
Transluscent display panel;
The backlight that limits in the claim 1; And
The backlight control system that comprises motivation value generator according to claim 1.
12. display according to claim 11, wherein said display panel comprises the LCD panel.
13. display according to claim 11, wherein said light source comprises LED.
14. TV that comprises display according to claim 11.
15. computer monitor that comprises display according to claim 11.
16. a method of controlling the backlight of display, said display comprises:
Transluscent display panel; And
Be used for providing the backlight of illumination to the dorsal part of said display panel; Said backlight comprises a plurality of respective sources that are positioned corresponding preset light sources position; Be used for to the corresponding lap of the dorsal part of said display panel illumination being provided according to corresponding preset light sources Luminance Distribution; Wherein can come the intensity that said light-source brightness distributes is carried out convergent-divergent, and the stack that the light-source brightness of wherein said corresponding convergent-divergent distributes have defined distribution backlight by means of the light source motivation value;
Said method comprises:
Dependence is corresponding to will the light source motivation value being provided by the brightness of image value of said display images displayed; Said image comprises the high-brghtness picture images part; This high-brghtness picture images partly has than the regional high brightness around the said high-brghtness picture images part; Said method also comprises makes said distribution backlight show above that with given pace the hi-lite of the said display of said high-brghtness picture images part reduces gradually on every side; Said speed is independent of the position of said hi-lite with respect to said light source position, and the said hi-lite of said display has than the regional high brightness around the said hi-lite of said display.
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US8810501B2 (en) 2014-08-19

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